The invention relates to an applicator element and a method for electrographic printing or copying by using liquid ink.
Known devices for electrographic printing or copying make use of a process in which dry toner is applied to the latent image of a latent image carrier, for example a photoconductor. Such dry toner results in relatively thick toner layers since the toner particles have a relatively large particle size and a plurality of toner particles has to be deposited on top of each other for achieving sufficient color coverage. The dry toner layer applied to the latent image has to be fixed, this requiring a relatively high energy. This high energy leads to a high stress on the final image carrier, preferably paper, as a result of the fixing by means of heat and/or pressure.
Liquid toners that have been used up to now contain a carrier liquid that is odorous and inflammable. Often, the final image carrier to which the liquid toner is applied is likewise odorous. When liquid toner is used, it is brought into contact with the latent image carrier.
U.S. Pat. No. 5,943,535 discloses the use of a water-based liquid toner that is brought into contact with the latent image carrier. Owing to the conductive liquid toner, a deposit corresponding to the electrostatic charge image is formed on the latent image carrier.
Furthermore, reference has to be made to conventional printing methods, such as offset printing, which use liquid ink. With these conventional printing methods, the print form is not variable so that economical printing of small numbers of copies is not possible.
DE-A-30 00 019 discloses a device for a liquid developer. A latent image, for example a potential pattern, is generated on the final image carrier. An applicator element carries a liquid layer. An air gap having a predetermined air gap width is set between the liquid layer and the final image carrier. Liquid elements of the liquid layer are transferred onto the surface of the final image carrier due to its electric potential.
U.S. Pat. No. 4,982,692 discloses a method for printing that uses a liquid developer. Under effect of an electrostatic force field, droplets of a liquid layer on an applicator element are transferred onto the surface of a latent image carrier.
Further, U.S. Pat. No. 5,622,805 discloses a method using a liquid developer in which method droplets on an applicator roller are transferred onto the surface of a latent image carrier under influence of an electrostatic field.
U.S. Pat. No. 4,942,475 and U.S. Pat. No. 3,830,199 disclose liquid developer systems, in which an applicator roller carries a liquid layer. The surface of the applicator roller has a plurality of recesses in which the liquid developer is contained.
JP 10-18037 A with abstract discloses an image generating method, in which a contact surface presents a carbon film. This carbon film is comprised of DLC material that is generated by a plasma CVD method.
An object of the invention is to specify an applicator element and a method, in particular for electrographic printing or copying, which allows the use of liquid ink.
According to the invention, an applicator element and a method provides a layer of liquid ink for inking a latent image carrier in a device for electrographic printing or copying. A surface of an applicator element is prepared such that it has a structure with a plurality of areas at which detachment of droplets from an applied liquid layer is facilitated. The plurality of areas comprise first areas with increased electrical conductivity, second areas having a surface energy that is varied with respect to a remaining surface, and third areas formed as microscopic elevations on an otherwise smooth surface.